Like baqai said partition magic, I use it myself and often you dont even need to restart and it will create partitions really quickly without rebooting, the only time you have to restart is when doing stuff to the windows partition.
You can use fdisk too, I think you can create a dos/fat32 partition and then when you go to into xp install fromat it with ntfs which id assume you would use? and go on with the install. I havent used fdisk in a while, but you can run it off a win98 bootup disk which can be found at
www.bootdisk.com